Electric clock



April 8, 1941. R. P. LANDGRAF ELECTRIC CLOCK Filed July 24, 1939 Patented Apr. 8, 1941 ELECTRIC CEQES Richard l?. Landgrai', Chicago,

Application .Ylily 24, i939, Seriali No.. 286,12@ l (Gio 6 Claims.,

My invention relates in general to electric clocksB It relates more in particular to a conrbinatlon with an electric clock of improved means for indicating when the clock is running.

Electric clocks propelled by small synchronous motors are either of the self-starting or non- Seli-starting type. In general, the latter is preferr-ed. Self-starting clocks have an advantage in that if the current is interrupted for a short period of time, they will again start themselves Without human agency. They have a disadvantage in that they may be found to be running and still show the incorrect time. It is customary, therefore, to place some indicating means on a self-starting clock to show whether or not the current has been interrupted. If it has been interrupted, the user of the clock finds it necessary to reset it.

If the non-self-starting type ofclock is operated on a source of alternating current winch is interrupted, the clock stops permanently. This compels the user of the clocl; to start it againl manually, and in so doing he will set it to the right time. Although certain advantages are possessed by the non-selfstarting type of clock in that if the clock is running at all it will always show the right time, it is not always easy to determine at a glance whether or not the clock is running. As a rule, some type of flasher mechanism is employed, usually comprising a varicolored disc rotatable with one ci the mechanical shafts and visible through a small aperture in the face of the clock. Even when the light is good, it is sometimes necessary to look closely to determine whether or not the flasher is operating and when the light is bad or the observant is some distance away, it is very diillcult to determine whether or not the clock is in operation.

According to the principal object of my invention, it is the provision of an improved means for determining when the clock is operating.

Another object is the provision of such a means which may be employed on either a self-starting or non-self-starting type of clock.

Another object is to utilize a pendulum which tends to swing of its own accord, wherein a small increment of power is employed to maintain the pendulum in operation.

Another object is the provision of improved means for employing a pendulum mechanism with an electric clock whereby to tell an observer at a glance whether or not the clock is in operation.

Other objects and features of the invention will be apparent from the following detailed scrlption taken with the accompanying drawn/rgD wherein Fig, l. is a face view showing a portion of the clock assembled without the casing;

Fig. 2 is a side elevational View thereof;

Fig. 3 is an enlarged fragmentary sectional view taken on the line 3-3 or Fig., i; and

Fig. l is an enlarged view talren on the line li-t o Fig. 3.

Looking at Fig. 3, I show a usual type o dial face lo, hands il and i2, and a relatively small pendulum i3 mounted to swing on the anis ci the hands as a pivot. The pendulum is commensurate with the hands in size and may be nished a relatively bright color so that it may be least as noticeable or possibly more noticeable than the hands themselves. The clock face shown in the drawing is a relatively large one as may be readily determined by comparing it with the size of the synchronous motor and movement in lig. 2; consequently the pendulum mounted en tirely within the connes of the dial face is rela tively large enough for my purpose. llt will be understood, however, that ll may mount the pen dulum diderently, particularly when a relatively small face is employed on the clocln I shall refer briey to the mechanism as shown in Fig. 2 to illustrate a preferable form of drive for continuously imparting sufiicient power to the pendulum to maintain it in operation.

An alternating current coil M, adapted to be supplied with current from a suitable source, has a core l G connected with pole pieces il (the drawing shows only one, although two are customarily used) forming the stator of the motor. A rotor shown in dotted lines at I8 is connected to a rotor shaft la. This rotor shaft carries a pinion 2i meshing with a gear 22 carried on a shaft 23. This shaft 23 supports a worm 25 which, through a suitable gear train including the usual twelve to one time train, drives the hands at proper differential speed. The hands are mounted on the usual time shaft 26 and stud 21 customary` in the art.

Now as to the operation of the pendulum, I employ a sleeve 28 which projects through the dial face and is journaled on the time stud 2l. The portion of the sleeve 28 extending beyond the face I0 has a. pendulum i3 secured thereto.

Within the mechanism. housing, however, I support an arm 29 provided with a longitudinal end slot 3i. A relatively small'crank 32 carried on the shaft 23 engages in this slot and as the shaft 23 rotates carrying the crank 32 with the arm 29 and sleeve 28 are reciprocated about the time stud 2, thus also imparting a :reciprocating pendulum-like swing, to the pendulum i3.

The/pendulum may, of course, be made to swingat any selected frequency. In the design ofl clock mechanism in which I employ my pendulum, the shaft 23 makes one complete rotation every second. Consequently, the period of the pendulum is also one second; that is to say, it takes one second for it to make a'complete swing back and forth from one side to the other. By selecting a pendulum whose natural period is substantially one second, the pendulum tends to move itself and there is very little power required to be imparted to it through the crank mechanism described.

Although I describe my invention in detail to permit those skilled in the art to practice it, it is obvious that I am not restricted to the particular form of the invention shown, but am limited only by the scope of the appended claims.

'What I claim as newV and desire to protect by Letters Patent of the United States is:

' chronous motor, a time train mechanism driven i. In an electric clock, a synchronous motor, a

time indicating mechanism, a time train mechanism receiving movement from the synchronous motor and connected to impart time movement to the time indicating mechanism, a dial face disposed between the time indicating mechanism and the time train mechanism, a pivoted sleeve extending through the dial face, a pendulum secured to the sleeve at one side of the dial face, an arm secured to the sleeve at the opposite side o the dial iace, said arm having a longitudinal slot therein, and a crank secured to a shaft forming a part of the time train mechanism, said crank extending into said slot whereby rotation of the shaft imparts a pendular movement to said pendulum through said arm and sleeve.

2. In an electric clock, a synchronous motor, a time indicating mechanism, a. time train mechanism, receiving movement from the motor and imparting time movement to the time indicating` mechanism, a dial face, a pivoted sleeve extending through the dial face, a pendulum secured to the sleeve on one side of the dial face, an arm secured to the sleeve on the opposite side of the dial face, said arm having a longitudinal slot therein, a shaft forming a part oi the time train mechanism and having gear connections to cause the same to make one complete rotation by said motor and including a. motor shaft and time stud, minute and hour hands secured respectively to the said time shaft and stud, a sleeve journaled on said stud and extending through the dial face, a pendulum securedto the sleeve and visible against said dial face, an arm secured to said sleeve, said arm having a slot therein, and a crank secured to a shaft forming a part of the time train mechanism, said crank extending into the slot in said arm.

fi. An electric clock as dened in claim 3, wherein said shaft forming a part of the time train mechanism rotates at a speed of one revolution per second.

5. In an electric clock, a .dial i'ace, a synchronous motor, a time train mechanism driven by said motor, and including a shaft and sleeve extending through said dial face, said shaft and sleeve carrying hour and minute hands respectively, a sleeve extending through said dial face concentric with said shaft and journaled on said mst-mentioned sleeve, a pendulum member mounted on the said last-mentioned sleeve and against the said dial face, a slotted arm on the last-mentioned sleeve behind said dial face, and a crank secured to a rotating shaft forming a part of the time train mechanism, said crank extending into said slot of said arm whereby to cause reciprocation of said sleeve and pendulum.

6. In an electric clock, a dial face, a synchronous motor, a time train mechanism driven by said motor, and including a shaft and sleeve extending through said dial face, said shaft and sleeve carrying hour and minute hands, respectively, a second sleeve extending through said dial face concentric with said shaft and journaled on said first-mentioned sleeve, a pendulum mounted on saidsecond sleeve and against said dial face, a crank secured to a. rotating shaft forming va part of the time train mechanism, an arm carried by said second sleeve and extending toward said crank, and mechanical means forming a connection between said arm and crank whereby to impart oscillatory motion to said arm and pendulum.

- RICHARD P. LANDGRAF. 

